This post applies to the ADV7280, ADV7280-M, ADV7282, ADV7282-M and ADV7283.
The deinterlacer block (I2P) is designed to have a minimum amount of latency between input and output (max latency is about 5 lines of video ~ 85 ms). This is important for automotive applications. Due to this it uses a line based deinterlacer algorithm to interpolate between lines to generate the missing lines e.g. in odd fields it interpolates between lines 1 and 3 to generate line 2.
Note that an analog devices proprietary algorithm is used to smooth the picture to reduce the effect of low angle line artifacts (jaggies). However such artifacts can still occur.
If you wish to have output video without deinterlacer artifacts, I advise using a decoder that used a frame based deinterlacer. This will add significant latency and cost to your system. The ADV7186 or ADV7850 can perform this frame based deinterlacer.